The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Generally, in order to use an information technology (IT) environment, a function is implemented by integrating elements such as a server, a storage, software, a solution, a line, etc., and solutions, such as a website, mail ERP, CRM, etc., are developed. The inventor(s) has experienced that in such development, the introduction of software and the integration and customizing of systems are needed, and thus, it is required to study separate technology. The inventor(s) has noted that cloud computing technology has been recently developed in which an IT environment is constructed to enable the use of a service even without professionalism of separated technology and is usable.
Such cloud computing can be largely categorized into three fields: namely, (i) Software as a Service (SaaS) that provides a software application service as a service; (ii) Platform as a Service (PaaS) that provides a standardized platform as a service; and (iii) Infrastructure as a Service (IaaS) that provides an infrastructure, such as a storage, a network, etc., as a service.
A cloud storage system, one of the cloud computing technology, virtually makes different users' data appear to be stored in separate spaces, but actually stores the data in the same storage space physically.
The cloud storage system does not encrypt and store data itself when storing the data but encrypts and stores the data in transmitting the data.
On the other hand, the inventor(s) has noted that a function of encrypting and storing a document is necessarily needed for storing a document (for example, documents of companies) requiring security in a cloud storage.
However, the inventor(s) has experienced that the cloud storage system that provides a storage service for large-scale data causes overhead of calculation necessary for encrypting and decrypting data when desiring to directly support an encryption function, and thus, the use of many resources is needed.